1. Field of the Invention
The present invention relates to a connection cap and a cable connection method utilizing the same. The connection cap is used for connecting core wires of a plurality of sheathed cables to each other, so that the connection cap covers and holds a wire connection portion for insulation and waterproof protection of the connection portion.
2. Background Art
FIG. 5 shows a conventional one of such connection caps, for example disclosed in Japanese Patent Application Laid-open No. H. 10-243539.
In FIG. 5, a connection cap 50 can easily cover core portions 59a of jointed cables 59 without a troublesome work for surrounding the core portions 59a with an insulative resin material. The connection cap 50 has a cap main body 51 that receives the core portions 59a. The resin material, which is in an uncured state, is injected into the cap main body 51 to cover the core portions 59a and sheathes 59b of the jointed cables 59 so as to fill the cap.
The jointed cables 59 have ends of the sheathed cables, in which the sheathes 59b are stripped to provide an exposed core portion 59a. The core portion 59a has core wires electrically connected to each other. The core portion 59a is formed by crimping or welding before inserted into the cap main body 51. The cap main body 51 is made of an insulating synthetic resin material such as polyvinyl chloride, polyethylene, and polypropylene. The cap main body 51 has a rear end wall 52 at its distal end for closing the cap main body 51 and an opening 53 at its fore end for inserting the core portion 59a. 
The cap main body 51 has a retainer plate 55 near the opening so as to extend opposite to the insertion direction of the jointed cables 59. The retainer plate 55 prevents disengagement of the jointed cables 59 from the connection cap 50. The jointed cables 59 are secured to the connection cap 50 with a tape 57 wound on the jointed cables 59 and the retainer plate 55.
The connection cap 50 has a sealing layer 56 defined by curing of a material such as an epoxy resin and a polyurethane resin, and the sealing layer 56 is electrically insulative and serves as a waterproof construction. The resin material has a viscosity with 100 to 5000 cps (0.1 to 5 Pa·s) when received between the cap main body 51 and the core portion 59a. 
At an integrating step of the jointed cables 59 and the connection cap 50, an uncured resin is filled in the connection cap 50 before insertion of the jointed cables 59 into the connection cap 50. Thereby, the uncured resin intrudes between the core portion 59a and the cap main body 51 and between the sheathes 59b and the cap main body 51. The uncured resin also intrudes into clearances among wires of the core portion 59a by capillary effect. Then, the cap is kept at a temperature of 20 to 60° C. for 2 to 30 minutes, so that the resin is cured to secure the jointed cables 59 to the connection cap 50.
However, the conventional connection cap 50 involves a drawback described hereinafter.
The jointed cables 59 can not be correctly positioned in a radial direction (perpendicular to the insertion direction) within the connection cap 50 when inserted into the connection cap 50 with an uncured resin filled in the connection cap 50. This may cause a deviation of the core portion 59a from an axial center line of the cap main body 51. For example, when the resin cures with the core portion 59a contacting an inner surface of the cap, the resin intrudes insufficiently between the core portion 59a and the cap inner surface or in clearances among the wires. Accordingly, sealing of the core portion 59a is not surely achieved, decreasing quality and reliability of the connection cap 50.
Furthermore, the core portion 59a is defined by press-crimping, resistance welding, ultrasonic welding or the like. Such processes can not form the core portion 59a to have a circular section. It is disadvantageous that the connection cap 50 is formed to comply with the non-circular core portion 59a. 
The connection cap 50 is unreliably positioned relative to the jointed cables 59 before the retainer plate 55 secures the cables with the tape 57. Even after securing by the tape 57, undesirable unwinding of the tape 57 causes that the jointed cables 59 deviate from their correct position within the cap.